Calmidazolium is an imidazolium ion that is imidazolium cation substituted by a bis(4-chlorophenyl)methyl group at position 1 and a 2-[(2,4-dichlorobenzyl)oxy]-2-(2,4-dichlorophenyl)ethyl group at position 3. It acts as an inhibitor of calmodulin, a calcium binding messenger protein. It has a role as an inhibitor.